Triiodothyronine

Triiodothyronine, with the chemical structure of 3,5,3'-L-triiodothyronine, well known as T3 because of it's difficulty to pronounce is one of the main Thyroid Hormone produced from the Thyroid gland and controlled by the TSH form the anterior pituitary gland. T4 with T3 are the most important hormone that affects metabolic rates. they help regulates the metabolic processes which are essential for a normal growth and development of our body and the maturation of our brain cells.
t3 is 3 to 5 times more potent biological system thab t4 because one third of all t4 are converted to t3 during the course of it's metabolism.

Functions

• increased oxygen consumption


• growth


• development


• sexual maturation


• stimulation of heart rate and heart contraction


• protein synthesis


• carbohydrate metabolism


• cholesterol and TAG synthesis and degradation

IDEAL SPECIMEN: serum; plasma with EDTA or heparin may also be used

METHODS

• Direct Equilibrium Dialysis or Infiltration


• Determination of T3 by Radioimmunoassay (T3(RIA)


• Determination of T3 Uptake by Radioassay

Normal Values: 0.8 - 1.1 ug/dL

Clinical Significance:

• Primary Hypothyroidism - has damage in the thyroid gland and insufficient in hormone synthesis. Confirmation of the disease is the results where T3 and T4 decrease; TSH increase.


• Congenital Hypothyroidism - due to absence of thyroid gland or defects on thyroid hormone synthesis.


• Secondary Hypothyroidism - due to pitiutary or hypothalamic disease;

• Hyperthyroidism - can be caused by diffused toxic goiter, damage to the thyroid gland. T3 is elevated early than T4.

REFERENCES

Tietz Textbook of Clinical Chemistry Second Edition by Karl A. Burtis and Edward R. Ashwood

Fundamentals of Clinical Chemistry Third Edition by Norbert W. Tietz